Although they come in a variety of shapes and sizes, concrete masonry units are generally similar in design. Blocks are generally hollow units made of cement with hollow cores called cells. The outside surfaces of the block units are called face shells, and they are connected by cross webs. Each block generally consists of 2 face shells (inner and outer), 3 cross webs (one at each end and one in the middle) and two cells divided by the middle cross web. These cells are where the moisture/water problems occur. Water passes through the outer face shell settles and collects at the base of the wall in the open cells with no means of escape.
Despite stability and strength of masonry walls, water penetration in masonry wall design is a major contributing factor to the wall's overall performance and ultimately to the life of the wall. In the masonry trade nomenclature, masonry wall construction consists of two types of walls, namely a single wythe wall and a cavity wall. Cavity walls are designed with two wythes of masonry consisting of an outside masonry block unit course and an inside masonry block unit course. A “course” is defined as a layer of concrete blocks or other masonry units laid end to end adjacent to each other.
Furthermore, unlike the common definition of a “cavity” being an open recess, in the masonry trade, a “cavity” refers specifically to the longitudinally extending cavity which separates the two walls of a double wythe wall construction. In a standard cavity wall design, having both an inner and outer wythe wall, a flashing and a weep hole course at the base of the wall directs water which may penetrate the outer wythe back out away from the inner cavity between the two wythe block walls.
Devices have been proposed for draining water from the cavity walls, such as for example, disclosed in U.S. Pat. No. 5,230,189 of Sourlis, U.S. Pat. No. RE36,676 of Sourlis; U.S. Pat. No. 6,584,746 of Hohmann; U.S. Pat. No. 6,256,955 of Lilley; U.S. Pat. No. 3,019,560 of Hansen; U.S. Pat. No. 4,852,320 of Ballantyne; U.S. Pat. No. 5,274,968 of Pardo; U.S. Pat. No. 5,343,661 of Sourlis; U.S. Pat. No. 5,598,673 of Atkins, U.S. Pat. No. 5,860,259 of Laska, U.S. Pat. No. 2,934,931 of Johnson and also as sold under the tradename MORTAR NET®.
In contrast to double wythe cavity wall constructions, a single wythe wall design consists of only one wythe of masonry blocks, wherein each block has one or more hollow core units with hollow recesses known as cells.
The need for a product of the present invention is a direct result of standard installation procedure of masonry units in the construction of single wythe masonry walls. Blocks are laid one on top of another with a mortar joint separating each unit. This mortar joint, which separates the unit, is spread on top of the block webs on the inner and outer face shell when each block is laid. Mortar is placed with a trowel and spillage occurs when the mortar is spread, known as mortar droppings. These mortar droppings fall both inside and outside of the hollow block cells. The location of the droppings, which fall within the hollow block cells, is where the problem occurs. These mortar droppings fill up within the bottom cells of the base of the wall and clog up the cells, preventing drainage therefrom through weep hole drainage ducts.
Even with flashings and weep designs, the mortar droppings occur and clog any passage of water weeping back out of the wall.
It has been attempted to stop moisture penetration through single wythe walls with such materials as integral water repellent admixtures and surface applied coatings, which however have not been 100% successful. Even flashing and weep hole courses have been attempted with little or no success.
“Weep holes” are generally configured as water drainage channels and tubes, of all shapes and sizes, which for the most part all are each installed at the head/cross joint of the masonry units (such as blocks).
Efforts to prevent mortar debris from accumulating in hollow cells of single wythe block walls also include the use of flat trays, such as described in U.S. Pat. No. 6,202,366 of Snyder, and such as known as “Blok Flash”, which completely cover the open cell of a block. These flat trays do not extend upwardly within the hollow cells of each block. Substantially flat, slightly concave trays are disclosed in U.S. Pat. No. 4,910,931 of Pardue. However, since these flat trays are flat or substantially flat, they can accumulate a complete layer from side to side of mortar droppings thereon, cutting off water drainage from weep holes, thus allowing water to accumulate within the cells of the wall and to cause major damage to the block walls by seeping through the inner face shell of the single wythe wall and into the building.
BLOCKNET® is another new product which has attempted to prevent water infiltration back out of the open cells of blocks. However, BLOCKNET® has the same disadvantages as the other products on the market today. It is a system that is comprised of metal flashing, with a horizontal mesh element adhered to the top of it, which sits at the bottom base of the wall. Along with this is another thin vertical mesh element which must be installed against the backside of the face shell within the cell of the block.
Disadvantages with this product include the fact that the metal flashing, with a mesh element adhered to it, must be set at the bottom base of wall, prior to any mortar being spread. The first step potentially presents the major down fall. This means mortar has to be spread over the metal flashing with the mesh element located at the bottom of the hollow cells of each concrete masonry block. Mortar droppings will inevitably occur, and just the procedure of spreading mortar over the flashing, may clog the weep drainage device. As stated in Step 4 of the installation procedure of the BLOCKNET® literature, the next step is installing the mesh element in the first course of blocks, which must be installed against the face of each hollow core/cell. This then leaves the base of the cell open and unprotected from mortar droppings, falling and clogging the flashing and weep hole channel device at the base of the cells of each masonry block.
Another device is CAVITY VENT® of Masonry Technology Incorporated, which has attempted the relieving of water infiltration back out of the wall or block cells. However, this product also sits at the base of the wall with little or no protection from falling mortar droppings and debris from above. It is a corrugated material, with channels, which weeps water to the outside from the cell area of the block. But just as other devices fail because a lack of adequate protection from the mortar droppings caused by the spreading of mortar, this can fail also under mortar accumulation.
Another attempt to prevent clogging of weep holes in single wythe construction is disclosed in the “Mortar Net Block Drainage System” which requires a cavity wall construction of two walls spaced apart from each other, together with a flashing at the base course of the wall. The flashing separates the two-walled base cavity wall course from the single wythe courses above. But, the necessity for the flashing, at the base, causes a major weakness in the wall, because the mortar doesn't bond to the flashing separating the block courses.
At the same time it should be mentioned that single wythe block structures make up almost 50% of all masonry buildings today. Single wythe concrete block walls are one of the fastest, strongest, most popular and cost effective building designs in the construction field today coming in at about 30% less than cavity wall construction. Therefore, there is a need to prevent clogging of weep hole channels at the base of each single wythe masonry block course.